In case anyone else is interested, I reached out to Magpul to see if they'd sell me the pins and I got a pretty disappointing response. Like most of us I've bought my share their stuff and this is the first time I've contacted them with a request, one that I didn't think was unreasonable. I had a somewhat similar situation recently with ADM and they gladly sent me parts (for free even). I put a couple of my old sopmod stocks on the guns, guess the Magpuls will go in the parts bin for Christmas gift to NJ friends.
Thank you for contacting us.
Sorry it took us a bit to get back to you on this, as we have been extremely busy.
We do not sell or, send out parts for you to repair your stock.
Normally, we are happy to help in any situation in getting your stock repaired for you.
However, since you modified the stock to be used in a way it's not designed to be used, that does void the warranty of the product, so unfortunately, there won't be much we can do for you in this situation.
If you are not able to repair your stocks you may have to buy new ones.