Does anyone have any tips or suggestions as to where I can find "X-Wing scale" weapons? Not necessarily 1/270, but military models that have a reasonable size comparison to X-Wing models. I'm looking to replace a few guns on some ships (Decimator/YTs) and I'm making a Mad Max-style B-Wing and I'm looking for that Jerry-rigged feel. 40k stuff is cool but its obviously 40k, looking for more of WWII/nam and other sci if pieces and I don't know where to start.

Epic 40K, or other 6mm-10mm scale games (Dropzone Commander, etc.) will have more appropriately-sized bits.

Infinity minis have a lot of options, I think there's like 8 factions with different design themes, all sci-fi. The rifles are around the size of a B-wing's cannons iirc.

Dust has a WWII / sSteampunk / Mecha theme that could work.

Heavy Gear is probably about the right scale - the shoulder mounted missile racks could look good on X-Wing scale ships.

Flames of War is another possibility... the scale is much larger (roughly 15mm), but individual turrets and weapon systems could still work just fine. Additionally, a lot of vehicles are plastic, and thus cheaper than pewter/metal.