I took the head of a trmendous roadkill buck and I was wondering how to get the velvet to stay on the antlers for a long term period? maybe a shellac of some sort?

http://www.camohunter.com/bleach.html

I' ll need another way because I really don' t think I can get my hands on any formaldehyde.

If you take it to a taxidermist they can preserve it or make artificial velvet. Formaldehyde is a carcinogen and you should take a lot of precautions when using it.