Have to agree with CBG, the ONC charts are pretty useless. The Morocco charts are next to impossible to get, you have to write to some office in Rabat (could also be Casablanca, can't remember) to get them mailed to you. No idea if that works. I've got copies (made on an architect's plan copier), were current last year,
AFAIK they are still ok. Forget the usual pilot supply shops, they don't have 'em.
Landing in GMTT and getting a briefing is a good idea, Leclairage
especially as you WILL need the coordinates of the VRPs/corridors. Once you have this, marking up a Michelin map might really be the best solution of all, as the 'official' charts aren't the greatest either.
Bellyfluffer, Aerodynamics in Malaga have them and will lend you a kit for your trip if you fly one of their a/c.
CBG, how did you get on with 100LL south of Morocco ? (assuming that's the favourite tipple of your a/c, of course
) It's a trip I'd like to do, but have - so far - been informed, that there's no 100LL in Maurentania and only limited supply in Senegal.