This gOOgle search...
turbo boost sensor ISB Freightliner
...produced a number of hits, with
Big Machine Parts being one of the more interesting. The pictured one resembles the "nut" part of yours, and maybe the broken plastic piece still in its connector. But it refers to a later model 6.7 ISB. Still, they had an "Ask Us" feature that could help you, maybe even with that fan.
The search also turned up other sources, even Amazon, and some pictures (which I usually find very untrustworthy) and links to RV.net and other forums.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB