Neem Oil for lice? Kinda long sorry:(

Last Saturday we rescued a 8wk old guinea pig that we named Mollee, today when I had her out, I noticed black pinhead sized clumps on her fur (did not notice them before and I made sure to do a good check of her when we brought her home, and introduced and then later caged her with her new buddy Piggy, another female that is the same age). She is not itching and shows no signs of distress but I believe it is lice, and could it have possible come from the corncob bedding I recently purchased to put in their cage-I checked the bedding and see nothing? Our other two guinea pigs, Gyngeer (who has the corncob bedding) and Peppy (who does not) are also not showing any signs. Piggy is occasionally itching, but no more then normal, and I do not see these clumps on her anywhere. The problem is 1) I do not have an good exotic vet in my area, the closest one was my dogs vet, and the clinic almost killed him so there is NO way I am taking my poor guinea pigs there, and 2) I prefer only natural remedies and holistic medicine (especially now after my experiences with traditional veterinary care). So my question is could I use Neem oil or a bird lice and mite killer instead of Ivermectin or does someone know of something else I could use? Thanks in advance!