You cannot get "real" past test papers, unless you know somebody who has access to them. You can find out which organisation writes the 11+ for your area.
If the organisation is NFER for verbal reasoning, multiple choice, you can purchase familiarization papers written by NFER.
There are a number of publishers, authors who write 11+ preparation papers, but few of these map into the "real" test, resulting in children learning to answer questions that they will not see on the "real" test.
The best advice is to ask the LEA or school which papers they recommend for preparation.
I do'nt know where you are, but as an example:
Wirral LEA set two verbal reasoning multiple-choice papers of 80 questions in 50 minutes, they recommend NFER cornflower blue papers for preparation.
You can also use IPS papers to prepare for this type of test, but leave out H, I, K, N, O and S questions, because they do not appear in NFER familiarization papers.
E-papers similar to NFER format should be on this site by 12th October.