Ruger 10/22 (the std skinny barrel model) Academy Sports U$180
Muzzle Brake for 10/22 Ebay U$12
Well Airsoft P90 from Ebay U$30
Tokyo Marui P90 fake magazine Ebay U$25
Red Dot sight Walmart U$30
5inx12in 1/4 plywood from Hobby Shop U$10
1/8 steel rod from Hobby Shop U$1
Goop Glue HomeDepot U$4
Video on conversion is found on YouTube. Search for 10/22 P90 by taofledermaus.
You need a Dremel Tool with sanding drum and a saw for the plywood.
Fun to shoot. The New Orleans Swat Team had a hoot with it.