You won't find it all, or any amount of it, in any one easy place. The PH site above has good pics and some info. You also need to trawl ExplorersWeb for some past article they've done on Shisha.
By most accounts the first 2/3 of the route is easy, but long - a real slog if you're not using HAPs. Along a moraine, through an easy icefall up onto a plateau, across this and up an easy face to a col low on the north ridge, up the ridge, where most put a high camp.
The main thing to realise is that Shisha is not the easy peak that it was advertised as for many years. Most people were only going to the bump on the ridge west of the summit, calling it the 'Central Summit', but when the record keepers and stats people finally got it all sorted it became clear that going to that point is not climbing Shishapangma. Only the 'Main Summit' is the summit. There is only one.
To get to that point you have to either:
1. climb the regular route to the summit ridge, hit the bump then struggle left/east along the summit ridge on a cornice, soft snow, avo terrain until you reach the summit. Most people can't manage this nowadays.
2. at or just above C3 on the north ridge regular route, traverse left horizontally under monster seracs way above, in often deep/avo snow, then cut directly up between more seracs to hit the summit ridge east of the summit, or
3. climb some way up the regular north ridge but before hitting the summit ridge, traverse left up and across the north face on avo snow to come up close under the summit, as per the original 1964 Chinese route, which has been repeated, but rarely, or ...
4. climb the south face
So, this why so few people go to Shisha nowadays. It's too hard for commercially guided teams, it's hard and/or dangerous to actually get to the summit for anyone, and the Chinese can be a bit of a lottery regarding access into Tibet. This is why Manaslu is now more popular, even though in past years it was considered too objectively dangerous for most. Money talks ...
Maps? Google Earth is now better than any map. I have the Lanzou Institute map, which is nice, but not really needed.
Logistics? Try www.monterosa-nepal.com
or Asian Trekking, Iceland Trekking, Thamserku Trekking, or any of the other reputable KTM-based agencies for BC-only services.