I'm not finding any Oxbow Natural Science "treats", just supplements, the Simply Rewards are the Oxbow treat line. Chins really don't need supplements unless something is wrong with them. If they are healthy and you are feeding a good quality pellet only food, and hay the chin should not need anything else. If there is something lacking in the food you are feeding you are better off switching to a good quality food. At best they wont do any real harm, at worst they could throw the nutritional balance off and you end up with a whole mess of health problems. All of them are really more for if your chin has a specific problem, they are not treats, just like chewable antacid tablets aren't treats for humans, they come in favored so they don't taste bad, but that doesn't make them a treat.
I don't know if you just don't read replies or what, but you were suggested several safe treat options already.
http://www.chins-n-hedgies.com/forums/showthread.php?t=49366 Another option is certain herbs, like those sold on
Fuzzies Kingdom. Chinchilla's have sensitive systems, so you are better off keeping everything as simple as possible rather then going with overly processed preservative filled treats. Pretty much all treats sold in pet stores are not really healthy for chins. If you just refuse to get anything other then commercial treats though, looking over the Oxbow Simply Rewards line, the only one that looks like it might not be
that bad is the Timothy treats, but I'd limit it to one a day at most (the bag says up to 4 a day).