Avon's Magix is fairly well-reviewed, although its pore-hiding abilities aren't consistent from person to person... I personally haven't used it (I live in Brazil and my gel-based sunscreen works well as a primer for me). I really liked the Clinique pore-minimizer (from what I remember, it's been a while), but Avon is definitely less expensive and may be worth a shot.
[just a clarification: Monistat's Anti-Chafing Gel is based on silicones (like Dimethicone and Cyclomethicone). It's not the same as the Monistat treatment gels, which are medicated with Miconazole Nitrate--an antifungal medication used for yeast infections--and are not safe to use on the face without a prescription. The Anti-Chafing Gel seems ok, though.]