I took a regular glass hood for a 55g that was too wide for my 60g to a glass shop, and they cut all 4 pieces to size for less than $5. I believe it was $1 per cut.
As long as you measure correctly (or bring a template), a glass shop should give you a perfect sized outcome. It's what they do professionally. If they couldn't manage something so simple, they wouldn't be in business very long.
Home depot has a tendency to be up to 1/2" off with wood & glass cuts, because they cut glass and wood free of charge as a matter of convenience, not precision. The cutters are far from experts. Although, a cardboard template should make it much easier for them to hit their mark if you do go that route.