My Purchases for Android is an easy way to find your app purchases
The problem is that your app history through the Play Store itself will let you find your purchases, but it also includes all of the free apps that you've installed, which can make it much harder to find the purchases. Newer versions of the Play Store allow you to remove apps from your history, which would clean it up, but it still requires a fair amount of work on your part to cull your list. And, even once you're done there's no way to sort the list, it will always show chronologically.
My Purchases theoretically fixes this whole issue, although the description does say that "Google keeps the list limited at some point", so there is the chance that not all of your purchases will show. Still, it should be a much easier way to find an app you purchased, and it does support multiple Google accounts. There is an ad-supported free version of My Purchases, or a pro version which will remove the ads for $1.29.