Just some places to get started looking for new clothes:
http://www.jhornaday.com/ specializes in 19th styled shirts (& skirts) for hot weather. This very modern fabric is supposed to offer superior wicking and cooling.
I wore mine in Honduras and although I cannot say that I felt cooler I was not as miserably hot as I expected which may mean that it was doing what it was supposed to do. This fabric does seem to keep me warmer in Alaskan winters than cotton does. The fabric is slightly stretchy like polyester and not stiff enough for me successfully attach a starched collar. The sleeves do slide up easily but could stand the addition of false buttons or cufflinks.
Watch for their fairly frequent sales.
Speaking of sales:
Type Coupon Code FREESHIP ( in shopping cart Window)
Hi Folks. Hope you have a wonderful Easter Weekend. We haven't done Free Shipping in a long time , so I encourage you to take advantage and save a few Bucks! You must type the coupon code in the box to apply though.
Free Shipping Last until Monday and there is no Minumum purchase.
Wahmaker clothes on Amazon: https://www.amazon.com/Wahmaker-Scully-Mens-Wool-Vest/dp/B00G1SVV76
Wahmaker seems to produce the sturdiest, best fitting, most flattering, buckle-back trousers available today. I wish my mundane pants were as comfortable. Their sizing is very consistent so once you know what you wear they are easy to order or even buy off Ebay.
http://frontierclassics.biz/clothing/ is still sturdy, priced even lower, but their sizing seems inconsistent so I recommend only buying off the rack where you can try them on. Their vest can be nice and their shirts are sometimes thinner and cooler while still pressing pretty well.
Check out these hat sellers:
http://www.buyrevi.com/ is having a $5.00 off special. Just apply coupon code Five Off when checking out so if you have been wanting some cooler SP clothes on the cheap this is your chance.
https://www.milanoo.com/Buy-Steampunk-Clothing-c1407 I have heard mixed reviews about this clothes seller. They are very inexpensive but buttons off fly off the first time that you wear their clothes. One practical gentleman simply re-sews the buttons immediately and is otherwise happy with the quality for the price.