Len, if the bushing in this Shimano pulley had an OD roughly equal to a common drill size, then perhaps you could drill this hole size into a small block of metal, then insert the bushing and compress the block in a vise to hold the bushing stationary for drilling.

I'm assuming here that the bushing is not so terribly hardened, at least in the vicinity of the hole.

Similarly, if you have a lathe, a chuck might be able to grip the outside of the bushing, but the surface is one that you don't want to damage in the slightest or you'll have to re-finish the OD and it'll end up smaller, not good for shift quality.

A machine shop could also do a run of bushings, which should be made of rust-resistant steel imo.

I've sourced quite a few Huret ball-bearing pulleys from Schwinn-Approved/Allvit derailers for use with Simplex and Suntour derailers, but I would keep a good Allvit intact for it's increasing market value.

Am I missing something or…
What about this guy?
He has lots of Simplex pulleys.
Vintage LJ Simplex Bushing Style Idler Pulley Set | eBay

Looks like has at least 7 or 8 of them ("from old barn"). I didn't like them for the price AND THEY ARE OLD. $20 for old delrin plastic......???? That is why I picked another plan to replace mine.

Those are also the older, offset-style pullies, for use only in the older-style cage. Early-1960's and possibly a few years extra before Simplex pullies all went symmetric.

Ah, OK. How can you tell the difference between the ones made for offset style and the other, non-offset style Simplex pulleys,
If I may ask? What are the differences? Thanks.

Look at the seller's photo of the pulley hanging on the screwdriver, the asymmetry is obvious there.

I had to replace one pulley on my SX630 and found the ones from a beat up 70's Shimano Tourney derailleur crossed over perfectly.

I used some new Tacx sealed bearing on my SR derailleur as they come with a boat load of different size spacers and worked great. I got tired of looking and didn't feel like paying stupid prices for some Bullseye wheels.
https://www.tacx.com/products/extra/jockey-wheels

O.K. final follow-up on finding/making a replacement rr derailleur pulley.

Got my Shimano pulleys today. The sleeve bearings have a very small diameter with a resulting bushing wall being only 1.38mm thick. IF it could be drilled/reamed out to take a 6MM bolt that would leave a .995mm sleeve wall. Doesn't really matter anyway because the sleeve bearing is hardened steel and my drill could not touch it.

So plan 'B' ..... modifying a CURRENT Shimano pulley is not workable (at least for me)
Plan 'C' is using Bullseye pulleys. Ball bearings just like my 1972 Huret rr derailleur.

Shimano and Campy, etc., used 5mm bolts so the bushing OD could be smaller and thus reduce the radial distance at which frictional forces acted.
Smaller radius means smaller torque for a given frictional loading, btw.

As we've all mentioned, there are many good choices of old derailers from which 6mm bolt pullies can be sourced, including earlier Shimano derailers as pointed out by scozim!

I've used many alloy pullies with good quiet operation IF the bike's chainline is "good" and IF the derailer and hanger alignment are as they should be.
Some of the aftermarket 10t pullies have alloy center "hub caps" that fit within very large-ID thin bearings, allowing the user to drill out the alloy hubcaps to 6mm, and I have done this myself.
Alternately, many alloy pullies have 6mm ID bearings which are intended to be sandwiched between thin washers which are included for shimming purposes. The hat-shaped sleeve-washers are the "reducer" bits that won't be needed if a larger 6mm bolt is used.

Now I am curious as to what the OD is of those early, 6mm Shimano pulley bushings(?).

If they were stored in a proper environment I think they'd be OK. $20 is reasonable compared to what some pulleys cost.

Ah. Got it. Thank you dddd.

I wonder, are any of that guy's offerings correct for a Super LJ ?
I guess maybe the ones in the cage?
Wanna make sure I buy the right ones.

As far as I can tell, the pulleys used on the Super LJ's are the same as those used their lesser models. I use Bullseyes with two washers on each side on my SLJ 6000 and SX610's.

Thanks GB. Guess I'll dig out my buried Criterium and see how they swap over.

Some Criteriums have the ball bearing pulleys.