It is possible, I have had a bit of a look around and not found any that have been the right size so far though, try local toy shops and maybe even a museum. The only problem is they are a lot less detailed than GW figs and usually the wings are a lot longer, so you might need to trim down a bit and do a little GS work to get them looking good.
Aside from that.. You can try making flying skinks/saurus as a couple of people have done. You can occasionally get them cheap on ebay, but I have found them a bit rare there too.