>>6732714I got a little creative with mech torsos, drilled a hole in the middle to seat a bit of 3mm sprue, plugs right into the upper back port.
Top left is a 1/144 scale Barbatos kit, bottom left is a FA Gourai
If you're not willing to mutilate kits like that, you can check out the Killer Beak and Propellant Tank Circle MSG kits, though I've found that they tend to protrude too far out from the back to my liking