Drop down menu options for products?

I am making a clothing / apparel site and I can't find a mod/tutorial for adding a menu option for products. Product size is what I need more than anything, this is crucial for shoes and any new shirts etc.

I tried convincing my client to just use separate products for each size, but she says it would look way to 'ghetto'. Ideally we would still add individual sizes separately somehow so that product quantity is tracked but still have them appear under the same product so that we get the menu option feature.

I have seen this on osCommerce carts but never on a Zen Cart, is it even possible? Any suggestions are greatly appreciated, thanks.

not sure if this is exactly what I am looking for but it seems like it:
https://www.zen-cart.com/tutorials/index.php?article=57

I followed the directions but when I got to the part of ADDING NEW ATTRIBUTES, and press insert, I get the error message at the top in pink: Attribute Option and Option Value Do NOT Match - Attribute was not added - : TEXT
:no:

Is there something else I should maybe try?