@Account Closed Your space is a nicer one that would typically be leased out by agents in the typical way. However since you are having zero luck then I am going to recommend older centers that are typically run by mom and pop owners techniques. I manage and lease some properties like that. Throw a couple of craigslist ads out there. Also a new one that has worked for us but requires more work is facebook marketplace ads. With these ads you will need to make sure that you are explaining leases better as you will be dealing with people that often do not have as much experience. You will also get a lot of people who want 1-2 year leases (which I am sure you don't want that short term of a lease). I have just had to lease out some small office spaces and I put an ad out on Loopnet, craigslist, and FB marketplace. These are spaces that go for around $1,000/mth modified gross and not as nice as your property, but still a nice small office building. The first of the 3 spaces I got leased thru the craigslist ad to a multi million dollar company. Typically this was my main way to get spaces leased, but this time it did not provide many leads. I got a ton of inquiries thru FB Marketplace. Only about 1/4 of those inquiries ever responded back to me. However I leased out the other two spaces thru these ads. The Loopnet ad provided 3 email leads and none of them every responded back to me after I replied to them. I got three spaces leased in less than 60 days.
This was my first time really trying the FB Marketplace ad, but it worked. You have to realize that there are lots of small mom and pop businesses out there that don't have a clue what Loopnet is. They drive around looking for a place and they look where they look to buy other things which is FB Marketplace. Big companies know to contact a commercial broker but not all mom and pop businesses do. The other thing is to make your sign on the street be very noticeable and very obvious that you have a space available. Most broker street signs just say available and stay up even when nothing is available so after calling on a few where that property is full they stop calling on them. Put a large and clear sign up that states how many sq ft the space you have available is. Something so they know it isn't just a generic sign. Perhaps even a feather flag.
These ideas may be the opposite of what any commercial broker would be willing to do, and will probably look down on them, however you have not had any success with their typical ways so give them a try.