WTB: Glock 20 10mm to .357 Sig conversion barrel.  I know it's a long shot, but if you have one sitting around collecting dust, I'd love to take it off your hands.  Email is in my profile.

Here is one available on eBay

https://www.ebay.com/itm/LONE-WOLF-GLOCK-M20-CONVERSION-TO-357-SIG-EXTENTED-2-PORT-BARREL-NEW/114403831569?hash=item1aa2ffef11:g:0DEAAOSw-Q1fUpgx

3-7-77  You might want to call RemSport Mfg as they were making some...
https://www.tr-enabling.com/product-p/ba-p-gl-20-357c.htm
Address: 566 Holyoke St, Ludlow, MA 01056
Hours: Open ? Closes 5PM
Phone: (877) 861-5992

I was able to get the Remsport .357 SIG GLOCK G20 CONVERSION BARREL  $115.00 on E Bay