It's hard to see from the picture, but a 5 MFD condenser is the same in modern description as a 5 Microfarad (uF) capacitor. I can't tell if under that in the image is a 25V rating, but you just need a similarly rated modern capacitor. Given the use case, probably any electrolytic should do a reasonable job, and going with a more standard value like 4.7uF should be fine as well.