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You can post on r/MechMarket or ask the creator here https://southpawdesign.net/collections/all if he will make one for you. Then you can ask on r/ergoMechKeyboard

I think for wireless you better look at ZMK instead. (Kinesis are coming up with a new split wireless model this year, but probably outside your budget).

Im not sure how much it will cost, and I don't think its fully released yet but the new Kinesis Advantage 360 Pro is roughly in this area.

ZMK rather than QMK though, checked price (not sure if final) but the model with the open firmware was $439 for their initial run.

Depending on how DIY you want to be you can possibly source all the parts yourself to save on (third party) labor costs. From handwired to fabbing open source PCB to asking a third party to assemble one for you.