I haute wondered if there is an aftermarket part to colt on that would allow for this. Have done it with the transmission.

Yep. There are a couple ways to adapt one from the oil filter adapter

The 92-99 Bonneville had an external oil cooler option with a sandwich plate and hard lines. The oil filter adapter is in a different spot than your car though. If you can find one of those, it might work on your 00+ H-body oil pan and oil adapter. It'll definitely thread on, I've just never seen someone try to mount and route lines with that pan/adapter.

The other option is an oil filter relocation kit. I have this setup with -10AN line, a Mocal remote oil thermostat and an Earl's cooler.

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95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.