Hi Paul,

You've pretty much covered the options here, although a good practice aid for improving your golfing muscles is a weighted club. Swinging one of these for 15 minutes a day will greatly improve the strength in your golfing muscles.
There are many on the market, here are some that I found:

1. Momentus

2. Swing Accelorator

3. Swing Trainer

Good Luck

Greg Hutton
P.G.A. Professional
golftuitiononline.com