I bought this Monistat Anti-Chafing Gel last week, and it's pretty good. But having had not tried the other, more expensive primers on the market, I can't attest to it being a dupe. I did, however, swatch-test my cousin's Smashbox primer yesterday, and although it's a bit thicker, the Monistat gel is pretty similar.
I'm oily-skinned and am acne-prone, and it's kept my oilies at bay and I haven't broken out either.
If anyone in Canada wants to give it a try, Shoppers Drug Mart currently has it on sale (unadvertised) at $5.49 a box. That's 50% off.
Happy hunting!