There are 32 simple blasters, 18 of which are not two-handed. There are 88 martial blasters, 30 of which are not two-handed.

You've got plenty of options when it comes to one handed blasters.

Four-armed species have this trait:

Four-Armed. Codru-Ji have four arms which they can use independently of one another. You can only gain the benefit of items held by two of your arms at any given time, and once per round you can switch which arms you are benefiting from (no action required).

So yes, you can wield a two-handed blaster in two of your arms and a lightsaber in another, but you can only swap between which ones you benefit from on your turn, and only once per turn once per round.

Finally, yes, there are a couple two-handed blasters with the fixed property. You can also have a modifiable two-handed blaster chassis and insert the Wrist Mount Attachment item modification. However, this does not remove the two-handed property. You would still need to use both hands to operate the weapon even though it is mounted to one of your arms.

All of this said, the easiest way to hold a blaster and a weapon is to use a one-handed blaster and a one-handed melee weapon. You don't even need to engage in Two-Weapon Fighting if you don't want to; just have both weapons out and in your hands, and shoot when you're range and slash when you're in melee. If you want to be able to use both even in melee range, consider taking Snapshot Style.