ok. here goes some info i found on mozart forum. if you want to read the entirety yourself click on library, articles, essays, and then choose mozart's music (left side), concertos - and there are several interesting ones about the subject.
here's what i gleaned: dennis pajot, you are a genius. the cadenza mozart wrote for schroeter's 4th concerto for harsichord or pianoforte(autographed cadenza) lays in the paris cons. of music. it was first listed in K2 as Anh 61a. can anyone get a copy of this for me???

three cadenzas K626a II were auctioned to a private collector. then in 1985 the autograph auctioned at southeby's. it had baroni di cavalcabo castiglione's name in the right column. about 1772 (dating by things mentioned in article).
i think i will look in the mozart jahrbuch for a reproduced autograph page found in milan that contains cadenzas for jc bach K107/1 and 2nd movts and also another cadenza (for another composer) which could have been for schroeter.
finding things is very difficult, but fun when you don't put time pressure on (as is the case when you have to get a paper turned in). seeing things first hand is very interesting!
NOW, final question. Does anyone specialize in form and analysis? once i get the desired cadenzas, i'm supposed to analyze them. HELP, HELP. i will read more about mozart's style of composition and keep posting for anyone else who is interested.