What has your experience been at the local Flight Standards District Office (FSDO) (Certificate Holding District Office - CHDO) been? 
They’re lazy, hate their jobs, are never in the office when you actually need something, will gripe over the smallest inconsequential detail and are paid handsomely to do pretty much nothing at all.
But thats just my “opinion”
In response:
The tail of the Government Civil Servant: Lack of motivation? Some resemble that remark!
Unavailable? It would appear that way when people show up without appointments! 
Anal retentive to the smallest details? Yes, guilty of it. 
An Inspector works by standards (be it regulatory/policy/procedures/specifications) and measures and evaluates compliance with. This is a large part of their job!
As far as pay, it is all a matter of opinion. The pay should be enough to preclude in possibility of compromises to those standards. (In other words safety pays and it pays to be safe.)
I can’t get them to come out and do a field approval.
Can you elaborate more? As you may already be aware, the Field Approval process has tightened up in the past ten years. That is to say, many Approvals had been issued in the past without meeting certification standards, or at least showing compliance with the required certification standards. Furthermore, as we have progressed from aircraft and aircraft engines that had been previously certified from the factory to meet the older Civil Aviation Regulations (CARs) we were given instructions to have Field Approvals meet the current FARs. That said, many FAA Memos and Orders were issued to eventually end up with a list of items that have to be forwarded to the Aircraft Certification Office (ACO) for FAA engineering evaluation and acceptance/Approval (usually the FAA FSDO Inspector gets stuck approving the Field Approval as the ACO engineer only accepts the data. That said, and not knowing your specific situation, I would recommend taking a look at FAA Order 8300.10, Volume 2, Chapter 1 “Field Approval”. There is additional information that I have in my office, but this should help in getting started. From there, mail the package with all the data possible to substantiate the Field Approval to the attention of the Airworthiness Supervisor (you can call the front desk to find out who that is). Then followup with a phone call. If all options have been exhausted and you have made a record of the dates and who you spoke with regarding this situation, then file a complaint with the office manager.
Without knowing the specifics of your situation, I do not know if I have helped. But, I wish you success.
As a former FSDO employee, I have to strongly disagree that inspectors are lazy and/or slobs!
The FSDO I came from was understaffed, believed in giving 200% of themselves to whatever the task, and wore dress pants/shirts and ties every day to work!
I’m sorry, they are UNDERPAID for the responsibility placed on them! I was there in ‘99 when the air traffic controllers got their humongous raise yet the ASI’s got nothing AND got their mandatory training cut! 
Their jobs are every bit as important as the ATC’s, and besides, the friggin’ planes don’t fly without the ASI’s work.
Thanks for letting me vent - now go out to your local FSDO and thank the first inspector you see!!!
A Proud but Former FSDO Puke