My boyfriends birthday is coming up, and he is always building things with electronics.
He modifies them, to make them bigger, and better.
So i was thinking i could get him something on the lines of that, but i have no clue where to look!

I seen a "build your own robot kit" but it was nearly a grand..

Any tips would be awesome!

Why don’t you ask him?
Not all gifts need to be a surprise.
I am sure he has something in mind already and maybe you can share in the cost.
Or perhaps he needs a new soldering iron, a new multimeter, a new probe for his scope, you get the idea.