Another option, if anybody's handy with metalworking, is to make your own chainring guard. I'm almost finished making my bashguard for my '73 Campy Strada crank out of 11g aluminum sheet, about the same thickness as the chainring. I'm never going to use the 54t outer 'ring and a guard for a 144bcd is obviously impossible to find. Of course you need all the metalworking tools and even then getting all the holes lined up, filing and grinding, etc. is a real pain in the rear but it does look good!
You can take 44t or 48t chain ring and grind the teeth off.
The ground ring is supa nice! I removed my f-dérailleur so I needed new smaller chain ring bolts or\ and a bash guard. ( riding my middle 36 t) am going to find another to mod and sandwich the ring to prevent chain jump. (2 bash rings would have set me back 80$) And these are lighter.
After grinding, I sanded to a rounder edge. ( I like the ring for stumps AND not having teeth gouges in my shins from messed landings.)
So no one called me on the obvious fact a 46 wouldn't fit on the inside
A special type of guard is needed, though I prob won't get one.
The mid chain ring has space to go to say 39 teeth, I'm going 38.
Way off road with heavy suspension bikes, the norm seems to go 34 teeth.
The idea here is to match your normal cycling speed to the chain line running to the middle of the cog set, in my case, I'm in too high a gear so a few more teeth up front and I'm sitting pretty.
The guard has worked good, took hits well, one pant\chain grab-though I haven't even tucked 'em in lately and no chain jump.
All said, I like the conversion and no dérailleur is nice, lighter and no noise\chain rattle when jumping.
yes, I was disappointed as there were no sparks, Ouch!
There was a groove on the back of the chainring, 3mm from the tooth valley and when the teeth were gone I did a final using the line as a more precise guide.
About 20 min work, and took a cm off the grindstone so don't do it with someone else's grinder. (Dads gonna flip!)
I guess you could cut the teeth first.