i've heard alot of good come from the muzzy zero effect. i shoot a ripcord and thats real nice it's aroun $90 and i think thats prolly a lil more than your lookin to spoend but trust me if you do alot of stalkin and walkin though thick nasty shtuff it's worth the extra cash. but other wise i know cabelas has plasic coating you can put on ther and they also have replacement sheathes for your drop away.
http://www.cabelas.com/cabelas/en/templates/index/index-display.jsp?id=cat600319&navAction=jump&na vCount=1&cmCat=MainCatcat21424&parentType= category&parentId=cat21424