Worx WX550L Reciprocating Jig Saw + Cordless Impact Drill WX270L (Make your own Impact Massage Gun) after 20% coupon $60
Sold by Worx eBay store. Use code JOE4WORX to get 20% off. Use it as intended, but this is a popular jigsaw to make your own Impact Massage gun. Many videos on youtube but this is a good how-to on other parts you need. Auction listing says limited quantities available.
$74 - 20% = $59.20 + tax
Similar to a Thera Gun or others. *Disclaimer...there are many arguments about 'safety' and comparisons to the real thing. Make sure you read up, but many have done this hack.