Thanks for the input, everyone!
I actually managed to find a place in Yuen Long not far from (but not actually in) Tung Yik Market yesterday that sells raw squabs for $35 a piece, which I thought was a reasonable price since online shops/apps were asking for more like $48-50 for a product that's forever sold out on the PnS app.
I forgot the actual name of the shop, but it's a tiny store right next door to the Park n Shop opposite the wet market.
I actually feel kind of silly over how the shop I got my not-yet-roasted pigeon from was right under my nose the whole time!