2 independent GFCI (or 2-pole GFCI) outlet in 1-gang box. Does that exist?
Generally speaking, unless you are making changes, you don't need to add AFCI or GFCI to existing circuits. That being said, GFCI is of potentially major benefit in the kitchen. As you have found, you generally won't find AFCI + GFCI in a double-pole breaker, and you also won't find a GFCI/dual-receptacle that supports MWBC.
Assuming you don't need AFCI, my recommendation is to add the GFCI at the panel - a double-pole GFCI breaker. That gives you the really important human-safety part.
The flip side is, you may not need the same GFCI protection for your dishwasher, particularly if it can be hard-wired. Actually, you may not need it for the disposal if hard-wired, but my gut feeling is that the disposal is (because you touch the sink and the switch when the disposal is in use) is far more of a real-world ground fault concern than the dishwasher. In which case the other realistic alternative if you really want AFCI is:

Double-pole AFCI breaker
Change the dishwasher from cord &amp; plug to hard-wired (which is usually a standard installation option)
Install a GFCI/receptacle for the disposal.

If you do this, you will connect split the neutral before the GFCI. Assuming black/red/white:

Black hardwired to dishwasher hot
Red to GFCI Line/Hot
White pigtailed to dishwasher neutral and to GFCI Line/Neutral
Nothing connected to GFCI Load