That looks nice, albeit not super quality. Perfect for getting the miles in.
Most shops that have been around for a long time should have spokes for that somewhere. 27 x 1 1/4 was a very popular size. Online, perhaps Spa Cycles, or maybe Freemans?
It's a shame, I gave away some 700c wheels that would have played a blinder on that. Those ones look to be steel, which is not as bad as it sounds although they're buggers when you go through a puddle - you can't stop! You just need to anticipate.
700c wheels may or may not be compatable with your brakes, there has to be enough drop on the calipers. If you can't get enough drop, you will have to replace the brakes as well as wheels if you switch to 700c, which TBH that doesn't make financial sense on a bike like that.
If I were you, I'd just put new spokes in and ride it as is. It looks comfy.