Where to get Felt replacement armrests?

Just google it. Amazon, Nashbar, etc. etc. There are a couple different sizes, thicknesses, double check that you have the right one.

local felt dealer would likely be the easiest way...

as for the bolts, buy some stainless steel ones in the same size, plenty of options online.

Other than for looks, why are you worried about them being rusted on?

besides them seizing up (as the op has found) being a pita... eventually the corrosion will compromise the bolts... or most metal.

You can check youtube for some video's of guys unwrapping their drop bars and most of the metal underneath looking like swiss cheese from the corrosion over time... I've seen it in person a few times, extremely gross (and dangerous)

Just to throw my two cents in and recent experience before I sold off my B16. Same bolts, rusted to the crapper. I wasn't willing to sell the bike in that condition. I think I was only able to remove 1 of the 4 bolts with an allen wrench. I drilled the tops off of the other 3 to remove the rest and then visegrips to rotate them off. I replaced them with the bolts in the link below because A2 or A4 flat head socket head cap screws in 6mm are hard to come by cheaply. But note, the bolts go into aluminum. Aluminum and stainless steel together can gall the threads. A good NON COPPER based anti-seize is important.

Fastenal does carry the correct length of screws if you have one close by with a large enough stock to carry them. Otherwise, shipping was something like $10 for $4 worth of screws....

Stay away from unmarked bolts, as they should be considered non-grade and not trustable for the arm rest.

http://www.ebay.com/itm/361355773747?_trksid=p2057872.m2749.l2649&s...