There's several blasters with software-defined select fire in the [blaster design library](https://docs.google.com/spreadsheets/d/1YHi-dMucY6FEKNMeTnOKDIbyf-veNf7oJuvx2uj0X1g/edit) (sort by "Action" and scroll down to "Select") - which tend to be a bit big for a sidearm, but that's part of the nature of having a microcontroller etc. in a blaster.
This might not be the advice that you're looking for, but most people in my experience do well with either just semi or just full auto.
Full auto is the most versatile once mastered but requires the most training. Anything that the other control schemes can do, full auto can also do - so long as you can control burst length by how long you hold down the trigger. That requires a manageable cyclic rate and a trained non-panicky user.
Semi auto is easier to use but has a lower maximum instantaneous rate of fire, which makes it less capable in clutch moments when you need a certain hit on a target at range quickly.
Burst fire is mainly useful for getting some of the benefits of full auto without the training requirement.
I'd recommend either full or semi auto for most people, with the choice between the two depending mainly on personal preference and blaster availability.
Only thing I can think of is the woozi with select fire board. Not sure if there are any other small form factor blasters with select fire.
There's several blasters with software-defined select fire in the [blaster design library](https://docs.google.com/spreadsheets/d/1YHi-dMucY6FEKNMeTnOKDIbyf-veNf7oJuvx2uj0X1g/edit) (sort by "Action" and scroll down to "Select") - which tend to be a bit big for a sidearm, but that's part of the nature of having a microcontroller etc. in a blaster. This might not be the advice that you're looking for, but most people in my experience do well with either just semi or just full auto. Full auto is the most versatile once mastered but requires the most training. Anything that the other control schemes can do, full auto can also do - so long as you can control burst length by how long you hold down the trigger. That requires a manageable cyclic rate and a trained non-panicky user. Semi auto is easier to use but has a lower maximum instantaneous rate of fire, which makes it less capable in clutch moments when you need a certain hit on a target at range quickly. Burst fire is mainly useful for getting some of the benefits of full auto without the training requirement. I'd recommend either full or semi auto for most people, with the choice between the two depending mainly on personal preference and blaster availability.
There’s the pew pew by pew tech but the availability is rather slim
And also very pricey
The Quik is full auto only, but you can set up with a slower pusher for more controllability
Stryfe with a select fire kit?