Try the Center for Archival Collections at Bowling Green State Univ. They have an index of news articles, letters, etc. published in Ohio newspapers during the war. Their site has only two letters cited for the 102 OVI, but one may be in your time frame. Hoepfully, this is the link: www.bgsu.edu/colleges/library/cas/cwar. If that doesn't work, Google "Blwling Green State" and "Center for Archival Collections." I checked the newspaper index, but not the other on-line indices. A very user friendly site. BGSU has some very useful archival material, but not, I think, for the 102nd.
Also, have you checked the archival holdings at Ohio Historical Society and at Western Reserve Historical Society?