Once in awhile I njoy riding this old Sam Benotto. It is a very light bike with high gears.
Lately it feels rough while steering. What bearings do I order from Nashbar, Harris Cyclery, etc?

You'll have to remove the bearing balls and measure them to be sure!

MOST headsets use 3/16" balls. Hopefully the bearing races themselves are not damaged, since these will be much harder to replace.

Get grade 25 balls (the best, lower number = better). Replacing headset bearings is a very cheap and very worthwhile maintenance. You can certainly buy these from your LBS rather than mail-ordering them. Every bike shop and its mom has them, and they're usually cheap (I think 5 cents/ball at my LBS).

That would be nice if it's JUST the balls that need replacing.
I don't know, it's kind of an obscure bike.

Well... if MORE than just the balls need replacing, then replace the entire headset unless you can find spare parts for it, which might take a lot of work for an old obscure Italian headset. In any case, you won't be able to tell what parts need replacing unless you open it up, remove the balls, and clean off the grease so that you can inspect the races closely.

The type you have is a notoriously bad style, with an adjustable race that is knurled rather than having wrench flats, which makes it hard to adjust properly. Furthermore, there is no dust cap on the top half of this kind of headset, so it's very easy to get dirt and water in it. If your bike has standard head tube and fork dimensions then a new headset will be cheap and easy to get.

yeah, that's what i want, just a whole new headset.
I've never had any problems with this part of any of my bike, so i am kinda at a loss.
I just want to order the right part(s) and replace it all.

What should I measure?

The parts to be measured are annoyingly inaccessible, in that you can't easily measure them without first removing the headset (which is a pain in the ass, and will render the bike unrideable)

However, you may not need to. Check out Sheldon Brown's glossary entry on headsets: https://sheldonbrown.com/gloss_ha-i.html#headset The only two reasonable possibilities for your bike are (1) ISO headset or (2) obsolete Italian headset. Fortunately, according to Sheldon, it's possible to simply replace an Italian headset with an ISO headset (since the dimensional differences are small).

If you need a 1" threaded headset, Nashbar has one for $15 that looks fine, with proper wrench flats and dustcaps: https://www.nashbar.com/profile.cfm?c...ded%20Headsets
Or you can get some Tange headsets for about $20-30 from Harris, which might look nicer since they come in silver. If you plan to do the actual headset replacement yourself, rather than taking it to a shop, read this thread on how to make a ghetto press: https://www.bikeforums.net/singlespeed-fixed-gear/115657-3-ghetto-headset-press-sale-55-pounds.html

Wow..Thank you very much Moxfyre, that's exactly the direction i needed to start figuring out what to do.
Not that i don't like shops but i get a certain satisfaction out of fixing things.

By the way i think this bike was actually made in either France or Mexico LOL

Yep! It may be that a few bearings and some clean grease will get the headset running smooth again, but if you're willing to change the headset it will be worthwhile. I agree totally on the satisfaction of doing my own work.

PS- If your bike was made in France, and by sadists at that, it could have a VERY obsolete and VERY non-standard French-threaded headset *shudder* But there's only a very small chance on that.