jcortiz there are a few threads on this already but I will spare you the usual forum flame and tell you the absolute best way to get an M&P 22 mag for a fair price.
1) Go to midwayusa.com
2) Navigate the website to the S&W M&P series of pistols
Smith & Wesson M&P | Semi-Automatic Handguns | Smith & Wesson
3) Find BOTH the 10-round (takes 30 seconds to convert to a 12-round mag) and 12-round magazines. 99.99% chance they are sold out.
Smith & Wesson Mag S&W M&P 22 Long Rifle 12-Round SS
Smith & Wesson Mag S&W M&P 22 Long Rifle 10-Round SS
4) On the page with the product find the "Notify Me" button. Click it and fill out the information.
You will get an email and/or text message to your phone when the product becomes available. As soon as you get that email, hit the website and order one. It is the only way I know right now to get one for a fair price with minimal effort. I would suggest creating an account if you do not already have one so you can quickly order.