hip pain

Question
I have a 7-1/2 y.o. cockapoo (looks exactly like her miniature poodle dad).  The groomer thought she was a full-bred poodle.  Rimadyl works well for her and the vet gives a 10-day supply at a time.  She is wonderful on it, but a couple days after it is gone, the pain returns.  

The vet says there is nothing less expensive for her and she takes 2 a day at $1/apiece.  I am having difficulty keeping up with the cost.  I am also concerned about side effects of long-term use of this drug.

Is there something less expensive that I can try?  Is there an over-the-counter NSAID that she can take, i.e. Motrin?  

She also takes 2 Tums a day for a sensitive stomach.  I have been giving her Rimadyl morning and night and the Tums in the middle of the day.

Thank you for your help.  I do not mind if you would like to post my Q&A on the message board.

Answer
I got this question twice, but I did want to clarify what I was saying about volume discounts - I meant for the Rimadyl....not the aspirin. :)

Many times, if the vet knows you're having trouble keeping up financially, they will help with some sort of discount - or maybe he'll have some samples.