Welcome to the Forum.
Ok,, as you've noted,, there aren't any removable grips. That's not to say there aren't options.
The cheapest & easiest is to get one of those rubber slip on grip additions. I have done that on my MKIII.
Next,, you can go the custom route. I have seen a set of "add on" panels designed to be mounted over the current grip area with some minor modification (read; drilling tapping & installing studs to hold them.)
Lastly, some folks have been known to strip the gun, taking the gripframe, milling it down flat,, drilling & tapping it for 1911A1 grip studs,,, and installing regular 1911 stocks.
I have found that my slip on does wonders for mine in filling up my hand,, yet removable to allow the ladies in my NRA WOT clinics I teach to use it comfortably.