I have a book called the Wills of Our Ancestors.
The place to look is the Centre for Buckinghamshire Studies, where I am sure you have looked, but it depends on where in Buckinghamshire you are looking for.
Apparently you can even get information from the Bodleian Library in Oxford, and Eton College!
The Consistory Court of Lincoln has information about Aylesbury and Buckungham.
I found a will I wanted to look at for 1860, and sent for a copy of it. The name I wanted had been crossed out, very early redaction! It was because it was a commoner who had married a lord. That's not in Buckinghamshire, by the way, just a bit of information that you will not need.
I think pre 1800, people who did not make wills still had to have a list of possessions and have someone to organise passing goods and chattels on to family, so there were quite often inventories even if there were no wills.
Which online sites are you on? I have both Ancestry and findmypast but I have just discovered that myheritage is quite good, too.