HI i would use a red dot as i find them better for pistol (unless your looking at long range work) AND they are smaller, and as you have to overlever the 45,you will have more of the gun to hold rather than the scope.
PS budget guns n tackle in colchester do a great tv type finder with different ret for £29.99, and they are ment to be great. Will be getting 1 tomorrow for my AK47.