We bought a Tushy brand, and it pulls hot water from the plumbing directly under the sink. If you happen to have a sink right next to your toilet it might work for you. I’m not especially handy and I found Tushy’s instructions very straightforward.
Thanks for the reply. I’m probably going to have to stick with chilly water. I can’t imagine how expensive it would be to re-plumb the bathroom for that. I’ll try to check Tushy again but, for some reason I always get distracted when I visit their website…