Haven't looked for cabinets in many years, I didn't realize how uncommon 4 Ohm 2X10 or 2X12 cabinets are. A quick Google later and it looks like there's not much current production. Maybe some Mesa Powerhouse still in stock but discontinued, Aguilar, Bag End, and Avatar are all I came up with. Avatar cost 1/2 as much as the others. I'm sure you could find some used, but then you will end up with a mismatched rig like mine. From my small sample I'd look at Avatar.
No experience with Low Down Sound but it looks like they build anything you want.
If you are confident in your DIY skills you could possibly convert a 610. According to this pic, Ampeg 610HLF has 3 2X10 chambers.
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Not difficult to add jacks and rewire if the proper replacement speakers can be determined. Some of the knowledgeable people on here may be able to help with that.