Or hit our resident sewer of quality nylon products. He might be able to sew something into an existing pack.
I think sewing in a molle panel would be easiest.....
Best part of those two options are top notch work by Americans in the USA.
Goruck is nice stuff too if it works for your needs.
5-11 Covrt 18. Used mine daily for two years In a plainclothes assignment to carry some gear. Needed something inconspicuous to keep in my vehicle. The secondary/front pocket has molle stitched in, and the whole pocket opens up for easier access to anything attached to the bottom molle rows. Very low-key look, but very functional.
I've got a 5.11 also. Not sure what model it is, but the whole inside is molle and you couldn't tell from the outside. Have it set up as a go bag kinda thing with a few days of essentials, medical kit, and a weapon or 3.
I've got a Kifaru Spike Camp... I wish it had more molle inside, and out.
I guess my point is that I love the pack otherwise and will likely make or purchase an internal molle plate insert like this one, here:
This Camelback 2 day pack has molle fitment inside / outside; it is well fabricated. The molle material is thin, strong and very nice, like Blue Force Gear quality.
I must say though, molle is getting to be really old school. Much nicer current design packs e.g. Vertx and Blue Force Gear, with velcro mounting panels that are just as secure holding inventory and afford a much greater orientation of the gear in space. I installed elastic 550 paracord in this one to hold climbing straps etc. that are not accommodated by molle pattern; hopefully, emphasizes previous molle criticisms.
Agreed on the limitations of Molle.... Elastic paracord on a plate is in a few of my specialized kits... Mostly medical.
The 5.11 hexagonal plate allows for a good number of mounting options.
I use this externally non descript Vertx EDC with Safariland ELS /QLS adapter plates with blue plates fabricated from electrical box polymer plates (square / circular) with high grade velcro backing. This very secure system allows unlimited flexibility of kit orientation and of course re-configurable in seconds.
This Blue Force Gear Jedburgh pack is one of my favorites being a molle-velcro hybrid of sorts; having molle options externally with velcro panels internally.
The 5.11 gear with molle externally / internally also works pretty well when combined with Safariland ELS/QLS quick disconnect system. I have a number of
their bags in various sizes outfitted and it works nicely. A few examples.
The perfection of combining Safariland system with properly fitted packs is that you never have to leave any important gear behind, transfer it from pack / self to car to pack to self. Apologies in advance for the Serpa holster photos, but it was the only kydex security holster available at the time for firearm shown (Safariland finally made one).
Medical packs and such are configured with options to wear on operator belt (keepers) or transfer from soft to hard pack with Safariland system.
Small hard packs (e.g. Pelican) are employed to protect critical gear, some meds / sat phones / epirbs etc).