I've been cramming as much code to an Arduino Pro mini. I've tried just about every trick to save memory but I really could use more RAM/Memory.
I like the IDE, compatibility and small footprint of Arduino Pro Mini. What options do I have for replacement board that would have similar advantages but more RAM?
That is the smallest board I think. How much bigger can it be ?
The Lolin ESP32 is small, and also the Teensy LC is small.
You could show your sketch. Maybe we know a few more tricks.
Some libraries need a lot of memory, but sometimes there are alternative libraries.
What does the compiler say about the percentages for the RAM and the Flash memory ?
Start by describing the purpose of your project and its I/O device requirements. 
The ESP-12 is small and has far more memory than a Pro Mini but operates at 3.3 V with limited output drive and only one ADC input. It is very useful even if you do not require WiFi. 
I like the IDE, compatibility and small footprint of Arduino Pro Mini
If your into DIY there is this, my Pro Maxi PCB;
Atmega1284P, 8Mhz, 128K Flash, 16K RAM.
Deep sleep current 2uA
TPL5010 Nano power system timer option
FRAM option
MAX6006 AREF option
Pro Maxi V5.pdf (48.8 KB)
AdaFruit ItsyBitsy M4 has 192KB RAM.
newuser:
I've been cramming as much code to an Arduino Pro mini.
Pro Mega?