Moinmoin,
You could even do it manually, if You are experienced (or at least keen) enough to use a normal hex editor on a normal computer:
1.) Open the sysex file containing the whole bank or even both banks with a hex editor of Your choice
2.) Find the patch You look for
2.1) Every single patch starts with F0 01 23 02, let the hex editor search for that hex-string.
2.2) Somewhere in every patch You will somehow be able to recognize the patch name. It is not exact however, because there is a trick to pack 8 bytes into 7 as described in P'08 user manual page 54. So nevermind if the name seems a little bit corrupted.
3.) Extract the single patch You want or need
3.1) Extract the section starting with F0 01 23 02 and ending just before the next F0 01 23 02, the section will be 446 (decimal) bytes long.
3.2) Store this excerpt as a single sysex-file, use filename as You want as long it has a ".syx" extension.
If You want it to load exactly at the same bank/program as it was in the "big" sysex-file, leave step 4 and proceed with step 5. If You even want to reload the patch on a different bank/program, follow step 4.
4.) Change bank and program numbers
4.1) Open the sysex with the excerpt, it starts with F0 01 23 02 (remember: You made it to do so).
4.2) The 5th byte is the bank: 00 for bank 1 / 01 for bank 2. Change it to the value You want it to load into the P'08.
4.3) The 6th byte is the program number (unfortunately in hex): 00 for program 1 / 01 for program 2, ... , ... 7F for program 128. Change it to the value You want it to load into the P'08. You might use a function of Your hex editor to convert decimal into hex. Remember however, that the number You have to input here is "target -1".
5.) Load the patch into P'08
5.1) Start Your Sequencer or whatever file-transfer software You use.
5.2) Choose the newly created file with the excerpt only.
5.3) Send it to P'08 the same way, You would send the sysex with a whole bank or both banks.
6.) There You are.
HTH
Martin