I generally will wear a light wind breaker when carrying OWB, but sometimes, decorum calls for a more dressy jacket.

I'm looking for the lightest possible blazer type jacket, appropriate for summer also.

Anyone have any suggestions?  I have some suits but they are fairly heavy material, ok if in good air conditioning or the winter, but otherwise, stifling.

Price isn't that much of a problem, I'd rather buy once, cry once.

Don’t laugh at the model. I got this jacket a couple of months ago. It breaths, feels great and is light weight... plus it is now on sale

https://www.ferragamo.com/shop/us/en/sale-2/mens-sale/us-rtw-men-sale/g-716963

I always get the $99 or buy 1 get 1 deals at men’s warehouse.

Check LL Bean, I think they call it a travel jacket.

Very light, would look suitable with a tie or not.

Best of all, you can throw it in the washing machine, and let it dry on a hanger.

Before you empty your wallet, check the Goodwill or Salvation Army store.

They're often swimming in sport jackets, they're inexpensive, and after you pick it up from the cleaners it'll be like new.

You want minimal lining in a warm weather sport coat.  Look for terms like unlined, butterfly lined, quarter lined.

You should be able to find some clearance buys on these right now until the spring season stuff comes out.

I recommend Brooks Brothers and Spier & Mackay.  Bonobos also has an “unconstructed” line that would fit the bill.

https://www.spierandmackay.com/bottoli-blue-brown-check.html

https://bonobos.com/products/unconstructed-italian-wool-blazer?color=jamie%20cerulean%20blue&mrkgcl=1200&mrkgadid=3255058638&utm_source=google&utm_medium=PaidSearch&utm_term=387278000348_condition_new_product_type_suiting_product_type_blazers_product&utm_campaign=AAA_Merkle_Bonobos_Shopping_Brand&cvosrc=ppc.google.AAA_Merkle_Bonobos_Shopping_Brand_387278000348_condition_new_product_type_suiting_product_type_blazers_product&product_id=22852-BMC56-46S&adpos=1o4&creative=234265985964&device=m&matchtype=&network=g&gclid=CjwKCAiA3abwBRBqEiwAKwICAzl6m11hCs0R-Dr-KdZsGIEeRkifEUYqx9WD12vsnmyy493PiOK_iBoCYHkQAvD_BwE

Since thrift stores are always sparse having the right size and weight because "thrift store," I'd look for a travel jacket. Problem being, in the past I've generally seen these in khaki more often than not, which is a tell for "contractor" or "I'm carrying." Same as the old photographer's vest with that silly strap at the sternum. And usually washable, meaning, not ironed and scruffy looking.

Surfing "men's summer blazer's" there are a lot of skinny millenial's with the sleeves pushed up. Meh. "Mens light blazers" gets powder blue. "Mens travel blazers" gets more of what OP wants, "Mens travel jackets" pushes toward older Woolrich light mountain coats from the 80's.

Search terms will bring back varied subsets of choice, like socks it's going to involve more than a pair.  good luck.

I like these presentation jackets. Brown, Navy, or Black. They can be pretty casual up through professional depending on what pants/shirt/shoes you choose. They are a bit heavy for late spring and summer.

https://www.duluthtrading.com/mens-duluthflex-fire-hose-presentation-jacket-76257.html

ETA: I also have an OD green one from Target that is much lighter, but I can't find a link for that one. OD green jacket and khaki pants kinda screams operator (or at least park ranger) also, so it might not fit what you want.

Seersucker is light and cool.

I have been buying brookscool jackets from eBay .

They are only lined at the top, and light weight

Orvis.  Shop used on eBay.

This company has a good product, but a bad website.  It's a good company.  A Navy blazer works with almost everything too.

https://andersonlittle.com/

This will not be the most lightweight, but I prefer wool for both summer and winter.  It wrinkles less and is a bit more rigid for concealment.  In SC heat and humidity, YMMV.