Seems like there used to be more. But there is one RWH T-shirt on the "Shop" page, under accessories, at the bottom of the page. Seems like there used to be "Cathlete" shirts & "STS" shirts in the past. But new ones would be fun!
Just had a thought ... maybe Cathe et al could consider an optional "series" t-shirt and/or tank when releasing a new series ... sort of a bonus for initial purchases ... "limited editions" so-to-speak ... I'd seriously consider that as an add-on when buying a new series.
Funny you should ask this question. I've been really wishing they would have Cathlete shirts again. Mine are so worn. I've loved them to death. In fact I just looked down and realize I have one of them on right now but it is getting close to the point I have to retire it.