In my honest opinion, get a new helmet. I don't like the Troxel Sport helmets at all. They're just (not-so-dense) styrofoam covered in a bit of plastic. I wouldn't feel comfortable riding in one unless I was on a very very broke horse. That's just my own personal thoughts on the subject.
I really like the other Troxel helmets, and you don't have to break the bank to get a really good helmet. For example, Troxel Legacy helmets go for $90 in my area, and Tipperary Sportage Plus helmets go for $80. In my opinion, spending money on a good helmet can make all the difference.