It might be possible to modify the Grill you have (BBQ is a SLOW cooker Grill is a Fast Cooker) to work on a low pressure port but 1: the key word is MIGHT. and 2: I'm not going to even suggest how.
There is a device or two... In the old days they were made in Marshall, Mi. by Marshall Brass but I believe they discontinued and sold the designs.. Older folks at Most RV dealers will know the names though.
Extend-a-flow For Trailers and
Extend-A-Stay for motor homes Description of them
The first goes between your Propane tank and the hose to your regulator. in my day it had an POL male and female fitting (Today i suspect ACME) and a "Quick Disconnect" this is a fitting that looks a lot (exactly) like the top of a disposable propane bottle) It came with (or without) a 10' hose to your grill.. You could get an additional hose if needed and an adapter from the Quick Disconnect back to POL (or Acme today) if the grill needed that NOTE if the grill is designed for larger (Say 20 or 25 pound tanks) this may not feed propane fast enough.
The Motor home version did all the above with the addition of an INLET.. This comes, today with a 5' hose one end is about 1/4 inch threaded matching the inlet (Which by the way is both check valve protected and plugged) and an Acme coupler on the other end.
I had the first on my trailers and the 2nd on my motorhome.
A couple times I had to use external tanks to keep warm in the RV.
Worked great.
Pick the one that matches your needs. Self install. And use your current grill as designed.