Can't tell you specifically about a program, but I would look for a masters program. The USMasters swimming website is
United States Masters Swimming; adult swimming for health, fitness and exercise. Also, check any local USA-S or YMCA competitive programs, as many have associated masters programs.
I believe Marquette is home to Northern Michigan University? I assume you've checked into some kind of triathalon training group there?
Or consider starting one. Contact the local USA-S club if they don't have a program, and see if they'd consider letting you latch on to their program (could come with cheaper pool rentals, maybe something resembling coaching) if you could find a small group that was interested.
Masters programs are often full of swimmers with similar goals to you.
Best of luck to you in your training!