Your only option is to get that PCB or just get a Coolrunner CR3 Lite or flash a DGX to RGX and leave your system RGH but lose XBOX LIVE, but then you can play off USB hard drive.
You can also RGH it and get a D4S PCB for cheaper and just make a few changes in your hacked NAND image to work with the DVD key that was on the original PCB or get a Xecuter D4s PCB replacement.
Probably wont be any other way to do it unless its discovered by someone don't know if TX will invest time into finding another way or not because people have to buy 1-3 products of theirs to mod their drive now, depending on if they already have the needed tools on hand or not to mod the drives. The price will probably eventually drop to like $50, but it could be several months before that happens, the replacement D4s boards they released were initially highly priced $60-70, but after some months on the market the price dropped to $40-50 range and now D4S original locked boards are $30 on ebay, so I often use those instead if a system is RGH and needs a new drive or has a D5S drive in it.