In my quest to adopt those suggestions from the folks at Rivendell Bicycle Works that I agree with, but without spending a fortune in the process, I sometimes find very affordable alternatives that get the job done.
Here's another one.
Ron Chereskin seersucker shirts are now available for sale on eBay. The styles are older, with long cuffs and longer collar tips (remove the plastic stiffeners, they're pointless and they'll fall out when you wash them anyway), but they are all-cotton and seersucker and they DO keep you cooler on warm weather rides.
Rivendell was selling seersucker shirts, made in the USA, once upon a time.
They're nice shirts. I have one, an early prototype I got before they went up to almost a hundred bucks each. The shirt is maybe eight or nine years old now and has held up pretty well. But if I had to pay a hundred bucks for one today, simply couldn't do it. Still, I could attest to seersucker's ability to keep me cool on a hot day, so I began looking for more affordable alternatives.
I found these. Made in India from 100% cotton and sold under the name Ron Chereskin, they sell new on eBay for -- sit down -- $6.99 each.
They're funky-looking, with 1970s styling -- long cuffs and big collars -- but they are really
comfortable and I'm happy with mine.
NOTE: they run small. If you normally wear a Medium in men's casual shirts, order a Large here,
because they will shrink almost a full size when you wash them.
Find them here: http://www.ebay.com/sch/m.html?_odkw=&_ssn=selje55&hash=item23685ac752%3Am%3AmvRtcmZ-chXRscoZ8c_6OYA&item=152074635090&_osacat=57990&_from=R40&_trksid=p2046732.m570.l1313.TR0.TRC0.H0.Xseersucker.TRS0&_nkw=seersucker&_sacat=57990