I could be wrong but the base product appears to have the bog standard MC4 connection on a cable supplied. The usual solar panel kit looks to be 200 Watts. So with a 60V Maximum input how about this:

https://www.amazon.com/Flexible-Rugged-Surface-Motorhomes-Trailer/dp/B08M5PFNMV/

Connect these in series and with the open circuit voltage being 21 Volts that's 42 Volts so well inside what I see the maximum 60 Volt input to the Bluetti you linked to.

Sure you could cut the price by not going with flexible but camping means transport which could be harsh on a solid panel. To finish off you could make a stand or just put them on the roof of the van?