Balsa and other woods.

Hobby lobby
Hobby town
some Lowes Home Depot and similar big box outlets
Bigger JoAnns stores have a wood Crafts section that usually has a Balsa and Ply set of bins
Stunt Hanger Hobby has a very good selection of so called Contest Grade Balsa    https://stunthanger.com/hobby/
RSM sells rib sets     http://www.rsmdistribution.com/index.php
Lazer works sells a LOT of cut short kits...some expensive and some ridiculously cheap   http://lazer-works.com/misc.html
Brodak also sells about 72 different rib sets    https://brodak.com/control-line-parts/rib-sets-1.html


with the recommendations above and these--- you should have a few hours to spend perusing the web and local stores

Best to post  a general location and other cool bio info...we can better help if we have more to go by

Type in AC Supply, they have good prices and free shipping on orders over $100.00

Sig manufacturing has some good shapes such as plank airfoil, trailing and leading edges too.

Phil

I orders some airfoil from Sig and after 3 months had to cancel the order, apparently the had a fire and are rebuilding the wood shop

Hobby Town USA has a nice selection of balsa wood. You can buy online. Mark

Yesterday, I placed an order on line with Sig and today I received an email that 8 of the 11 items I ordered are out of stock for at least a month. I just asked for a refund and will order at a later time.
The items in stock were some tissue coverings.
The OOS items were airfoil balsa (3 sizes), butyrate dope(2), yellow tissue, castor oil (pt.), and 25% Champion fuel.
Didn't know about any fires there, but are the new owners in hot water ?

reading between the lines I suspect SIGMFG on life support and fading

Dan McEntee might have some insight

Michael's is another "brick and mortar" store in many cities that has a good selection of assorted balsa, bass wood, spruce, and ply. They are pretty expensive too. Did anyone mention Aircraft Spruce? They sell to modelers and full-size aircraft builders.
https://www.aircraftspruce.com/categories/building_materials/bm/menus/wp/index.html
Rusty

Balsa USA is my go-to online balsa supplier. Free shipping over $100. They will hand select specific wood for a nominal fee and do a pretty good job at it. I normally go to my local hobby shop for anything before ordering online. I want him to be around for a while. Tough business these days.