use of бы and же

I'm having a little trouble with these two particles. . .

я нервничаю и думаю, что же купить.
Он нервничает и думает, что бы купить.

The sentences were translated as

I am nervous and think what to buy
He is nervous and thinks what to buy

What then is the difference between бы and же here?

Difference is very subtle.
Both particles in this application are slight 'enchancers'.
In fact 'же' is simple 'echancer': compare "я говорил это / I said this before" vs 'я же говорил это! / and this is what I said (don't tell you don't remember)'. Man is worried and his worry is placed in this 'же' as is.
'что бы' is enchanced with some uncertainty. In some cases 'бы' is like 'would' (conditional mood), so it just emphasizes state of choice a little.
Both translations are correct.