One of the members of another site I am on (popupportal.com) works at Dometic and posted information about a special price deal on 5 Gallon Dometic/Sealand Model 976 Porta-Potti's. Full list is $180, usual sale prices is about $120 and, until the end of the month, a factory direct price of $35 + $15 shipping + sales tax is being offered. Here are the details on that sites original posting.
If you scroll down in the posting you will find a link to the installation and operating manual.
If the link isn't accessible let me know and I wil post the informtion here
Sorry, you can't order until regular business hours tomorrow.
Yes I ordered mine this morning