So I got a Pilot precise V7 RT (retractable) and it was nice but then I found the cartridge fits my Monteverde Riviera! I love the write of the Pilot precise but the weight and size of the Monteverde is a dream. Has anyone found any other cartridges/refills that fit other pens and make them a better write for you?

There are any number of 'hacks' available for many rollerball and ball points. For example, many different types of ball pens take Parker style refills. The Parker style ball pen refills are compatible with Itoya Aqua Gel and Visconti Gel Roller Balls, both of which are excellent. Often, when considering the purchase of a non-fountain pen, I let the refill issue dictate the purchase decision between two equally desirable pens.

I didn't know about the Pilot precise v7 Rt refill being compatible with the Rivieria - this would also make it compatible with any number of Schmidt style roller ball refills.