The AE Swede AirVenturi Avenger tactical frame is a great way to change the ergonomics of the Avenger. This was designed in house and professionally 3D printed by a firm in Utah, USA. Their resin behaves like a high strength polymer and holds up to UV light and environmental extremes incredibly well.
This includes the frame and 2 bolts to mount the frame to the Avenger in the stock mounting locations of the original Avenger stock for a solid fit.
You will need to buy separately a grip and butt stock to finish this as a kit.