That's going to be a little more difficult. I did a quick look at the spots as reported by DX Summit and the majority of the spots did not have the Maidenhead grid in the spot comments. If the Maidenhead grid was always encoded in the spot, then you might be able to search for that.
Another possibility would be to use
PSK Reporter to find stations on the air from the states you need.
Another suggestion...The ARRL is currently running a year-long Volunteers on the Air promotion. As part of the promotion, there will be stations operating as W1AW/portable from each state twice during the year. I believe that all of the W1AW/portable contacts are going to be uploaded to LotW. Many of those W1AW/portable activations are using FT8. The ARRL did the same thing in 2014 and I was able to complete WAS on both phone and RTTY by contacting the W1AW/portable stations. You can find the operating schedule here:
ARRL Volunteers On the Air
I operated as W1AW/9 from Indiana last week on phone.