The Shellhammer Family Web site at http://shelventure.com/
has a photo of a Foster Beisel who looks to be in the right age range as your Foster (I found this by doing a Google search for "Foster Beisel"). The Beisels on the Shellhammer site are from Drums, Butler Twp., Luzerne Co., Pa. From what I could tell by doing a quick Internet search, there was a Foster Abraham Beisel born in Drums on 30 Sep 1886 who later moved to Allentown. Perhaps the person who maintains the Shellhammer site could tell you who posted the photo and you could find out Foster's date of death from him.
The Lehigh County Historical Society maintains a Marriage and Death Extract file, which is an index of the marriage and death information from local newspapers, but the index only covers the years 1812-1873. The society's library does, however, have city directories covering the whole 20th century. See http://www.lchs.museum/Collections.htm
The Allentown Morning Call newspaper has an online archive, but the earliest of the articles it contains is from 1984. However, the obituary of at least one of Foster Beisel's daughters, Jean B. Wint, who died in 2005, may be found there. I think Gertrude E. Brunner, who died in 1987, may be another of Foster's daughters. To get to these obits, go to http://www.mcall.com/
, scroll down to the bottom of the page and click on "Archives." Then click on "Advanced search" and type in "Foster AND Beisel" (no quotation marks). Unfortunately, you'll have to pay for the full text of the obits; the site will only give you a short section of the obit for free.
Important note: Jean Wint attended St. Mark's United Church of Christ in Allentown. According to FindaGrave.com, there are Beisels about Foster's age buried in St. Mark's Cemetery in Allentown. So it might be worthwhile to look through St. Mark's records for Foster's death record.