Actually, I think I found it.
SOC appears to be the company, leaving
SD4 as the product name. Take a look: http://www.socfuse.com/products/pdf/P59_E.pdf
It's a time delay fuse - the wire on the inside will be a little twisty coil as opposed to a straight piece of wire. The voltage and amperage rating fall within the range on the data sheet, so I'm 99% certain that I've found the right fuse.
I'm no expert, but I've done a search on Mouser and here are possible replacements. Before purchasing, please let someone who knows what they are doing, like Olin or Russell, confirm or deny that the fuses I've found will work.
The parameters I set were 250 volts, 150 mA, Time delay, "Cartridge" style, and the dimensions.
Note: The actual dimensions of the fuse are 31.8 mm Length and 6.35 mm Diameter, which is the same as 1.252 inches L and 0.25 inches D. The search I performed on Mouser allowed fuses that were 1.25 inches L and 0.25 inches D as well, since it gave me more results. I'm not sure what kind of fuse clips you are using, so be aware that they might not fit perfectly, or at all.
Also, there were three "Midget" fuses from LittleFuse in the results that only specified the length as 38.1 mm. I don't know what the width is, so I'd advise against them, especially with a non-stocked lead time of 17 weeks.
Be sure to conduct a similar search on Digi-Key as well. I just tend to gravitate towards Mouser for some reason. But be sure to select time-delay fuse!