I agree with vbe, the best way is to look for a 2nd hand machine ( some will cost under 100$) and practice on it some.
You may drop by
Polarhome - gateway to freedom
They offer HP-UX Shells , But I'm not sure if they permit root access or not , I believe you may negotiate with them to get root access.
Long time a go HP Offered a program called HP Testdrive , I believe the program has been stopped I have found some articles on HP site stating that program is still up but under another name you may google it .
Also there are some sites offering some kind of temp access to practice machines for a fee.
Or you can setup a
vpar on your production system
you have multiple choices