Sometimes the internet will surprise you. On what started out as a search to find information for my last detailed industry post on Columbia Bedding, I discovered a listing of industries for the Kansas City area published by the CGW.
The source is a website dedicated to the Chicago Great Western. From that source I trimmed and saved both the full Kansas City Listing and the subset of that mentioning service by the SLSF. Now, not all of the industries on this list will apply to the Fairgrounds Branch, but it is still a worthy reference.
Several of the industries that I've profiled on this blog are listed in there, but unfortunately, the information does not help narrow down any dates. I'm guessing that the CGW industry listing presented there is an all-time compilation from many sources or a transcription of a single publication, just without the date.
Another source for industry information is the OPSIG Industry Database. There is some era appropriateness information included with this data source. A cross reference of it to the CGW source mentioned above pegs Battenfield Oil & Grease and Columbia Bedding in 1965. The source quoted there is "CGW", so it is likely that the OPSIG database includes all of the records from this same CGW source.
Speaking of the OPSIG, I highly recommend becoming a member. I'm an online-only member myself and for $7.00/year, it's a great deal!