Sippy cup vent

I bought lo 3 new cups a few weeks ago. He loved them and has no problem drinking out of them. This week all he will drink from are DS1's cups. DS1 need a few bigger cups, so I bought him new ones. Gave lo DS1's old cups. Now he wants the big cups. He has being screaming off and on for an hour pointing at DS1's cup. AHHHH!!!!  I don't want to buy more cups. At this point my cupboard has more sippy cups then regular glasses.