Cannot restore subscriptions purchased on another apple id--have looked for hours for a solution

I'm sure this has been answered before and I apologize for asking again, but I have not found anything that will let me restore purchases of two app subscriptions I purchased on my iPhone, which has a different apple id. When I first got my iPad, I had to also get a new @me.com apple id and I cannot change it now to match my other device. All of my apps sync regardless of which id they were purchased under, but when I try to "restore my purchase" in these two particular apps, I'm told I'm not an existing subscriber and need to repurchase first. Any help will be most desperately and gratefully appreciated!