Hi all. Just to follow up, I called up Egge and they were able to sell me one! Although they only sell the whole kit online, it turns out they're still able to sell the individual gaskets from it. Came out to just over $20 (plus shipping).
Here's their kit
https://egge.com/part/bst-1500-rs682g/, and the intake/exhaust gasket was the one posted by Jeff, PN 27026E from BestGasket.com.