If your just looking for the bolt you can get it here.
http://www.e-gunparts.com/productsch...del=1910z10-22 If you need the actual receiver, then you have two choices, buy a used 10/22 and take the receiver (Ruger does not sell this part as it is a serial number part) There are a couple places online that you can get receivers from, but you have to have them shipped to a FFL dealer as they are also a serial number part. You can check
https://www.volquartsen.com/product/...ement-receiver These receivers are about the best around...but they are spendy!