I am looking to purchase a ( synthetic ) blonde wig in a bob style for a shoot for under $100 and am wondering if this is possible and if so - where to find such an item

There should be a wig shop where you are located.  We have one near a high school and the owner sells a ton of wigs to the high school kids.  Most all of the synthetics are $29 in his shop.  Sort of interesting to rummage around in his and see all the styles and what is popular.  He must have 500 wigs in there and I've bought some with the mannequin head that also serves as a test subject.  They have the caps for wearing under them (cheap $2) to keep them clean.

He showed me some new ones and the synthetic is so real it is hard to tell it from the real hair and even fools him.  They weave the things a lot better too so a hairline part isn't a straight line and you can see the weave pattern.  They also have some newer heat-resistant ones that can be permed with an iron, but mostly just set with sprays.

Real hair and an exclusive wig shop can run a lot more even for bangs, but search out where the high schoolers go for their extensions, party wigs, graduation, and wedding stuff.  They ain't likely to be paying for some $500 wig.

If you want the synthetic hair, which is what you're looking at for under a hundred, to look more realistic you can take down the shine of the hair a bit with dry shampoo or by soaking it in liquid fabric softener and tepid or cold water for a bit. No heat tools for styling on fake hair. If you just want the straight bob, you can use styling spray made specifically for synthetic wigs. Revlon makes a great one.