Or you can post a "WTB" (Want To Buy) request here asking for a DBV-200 head, ID-044 SH for a Bally S5500. Post that photo of your old DBV-145 to help. We'll get your request moved to the Classified Ads area (free service) and it will maybe get you some responses from anyone with one for sale.
Your old DBV-145 was originally an "SG" but it is now an "SH" per the sticker in photo you posted.
A DBV-200 will accept more bills than the DBV-145 but the DBV-200 is still many years old and it won't accept all new style bills. For home use that should ok. Neither the DBV-145 or the -200 models are supported by JCM anymore, so there won't be any new software releases for either model.
The DBV-200 is a direct replacement for the DBV-145, but it will need to have the correct internal software to be compatible with your machine. That's what that "ID-044" is about. IGT, Bally, WMS, etc all use a different communication method to "talk" to the bill validator. I believe that your machine uses the same kind of DBV-200 that some WMS machines use (DBV-200 SH, ID-044). So someone with Bally or WMS bill validators might have what you need.
I don't think you will have to replace the DBV power supply on a Bally (on older IGT S+ machines you do often have to upgrade the DBV power supply when you go from a DBV-145 to a DBV-200).
As far as I know there isn't a software update available for your DBV-145 that will make it work with any of the new design US bills that are in circulation now. The last software released for it was ver 3.40 and that was many years ago, before all US bills (except $1) were changed. So even with that software update it would only work with the $1 bill, which has not changed design. Also, the DBV-145 only has one-way acceptance, the bills can only be inserted one way to get accepted (face up, top of President Washington's head to the right).
As Jay said, if you can get one or two of the old-style $20 bills they would probably work. That's what some people do, they just keep a few old bills for use with their machine. But those old bills can be hard to find.