Just Google and price shop. I couln't believe how expensive they have gotten in the last few years though! Ebay sometimes has overstock deals or gently used peds scopes. I ended up buying an ADC Adscope that is the same quality for much less money. With a little coaxing the Littman eartips fit since I only like those! Or, you can add an ADC head to Littmann tubing and earpieces, if you were going to get rid of the adult scope anyway, I know someone who did that. I got me ADC through Amazon for the best price I saw, you may want to check Littmann prices for their affiliates, too.
My personal opinion is that you can do a much better assessment on an adult or big kid with a pedi steth than you can do on an infant or toddler (or even cachexic adult) with an adult steth. Plus, it hurts less when you bend to pick something off the floor and it hits you in the teeth