I'd like to know if there is something I can do to close the gap or hide the gap in the blinds. Obviously, I can measure properly and purchase new ones but really trying to avoid that.
I've also thought about curtains, but it's also something I'd like to avoid. Are there any solutions to this?
Here is another photo zoomed out. 
Most places I've ordered blinds for will allow you to reorder a different measurement, up to a lifetime cap (like 4 times per person/household - you only get to fuck up for free so many times). The one I messed up they just let me keep because it was a custom size (still in my garage for some reason)
It's a pain but it is the way to go if you want your blinds to really be good for the space.
Only time I've been annoyed was a cloth roller blind I ordered to cover a large door window that I measured perfectly but nowhere in the description did it say that there was a 1/8 gap at each edge and the overall width of the blind was 1/4" shy of your measurement. Returned that one and just got a bigger one where the blind was the actual width I wanted...