I have a great idea for an upscale cupcake display but need 4 oz. clear, plastic straight sided disposable cups, not V shaped - must be "plum" for my idea to succeed. Have been searching buzz words on line like "portion cups" or "souffle cups" but they're all slightly beveled. Need other searching ideas..............oh I also tried candy cups. Nothing. Any ideas?

Try Googling cake shooter containers (they have straight sides and the pusher stick can be removed).

HTH

How about nut cups? Are those straight sided?

Could you make them with chocolate?
http://www.stockfood.co.uk/image-picture-Assorted-Chocolate-Dessert-Cups-678954.html
Could you wrap a pvc pipe with plastic wrap and put chocolate over it to make your cups?

Cordial glasses have straight sides.
If I had more of an idea of what you were going to use them for, I might be able to brainstorm more ideas.

LET ME KNOW IF YOU FIND THEM...I would like some also to pkg cupcakes in

You can also search on tasting bowl, cup or plate.

None of these are exactly what you are looking for, but maybe something will work. 

5oz, tall and narrow
http://www.bambooskewers.com/products/Cannello-Cocktail-Glass%2C-100-count-box.html

3oz square
http://www.bambooskewers.com/products/Quadrato-Cup-Seagreen%2C-100-count-box.html

4oz square, the description says straight sides, but they look slightly tapered in the pic.
http://www.bambooskewers.com/products/Tall-Quadrato-Cup-Seagreen%2C-100-count-box.html

4 Oz wine tasting cups, not sure how straight the sides are. They also may have a grove near the top.
http://www.massbarmate.com/product_info.php/cPath/29/products_id/206

This one doesn't have what you want, but there are some other neat things. If you can't find the others, perhaps you can find an alternative.
http://www.restaurantware.com/categories/Plastic-Smallware/

Thanks for asking this question. I love doing parties and found a lot of neat things drink this search.

The problem is that anything that has straight sides will not be stackable, which means that they are harder to ship/store. Disposable cups are probably not the kind of thing that people normally want to take up a lot of room storing, but instead want to be able to just keep a stack of the cups ready for use.

I suspect that you may need to look into items with other uses, like maybe vases.

How about these?
http://www.amazon.com/dp/B004FKAB2S/?tag=cakecentral-20

I literally Googled "straight sided cups" and that's what I got. Sometimes, if you leave your seach a little basic it returns more. Hope that helps.