A few weeks ago, Ray and his mom were talking about how our newest nephew is the spitting image of his dad (the baby's dad, not Ray's dad), who always wears suspenders. My MIL told him how she thought it would be hilarious to give him baby suspenders, which led to us saying, "Oh, we can find those online!" Turns out you can't find them for kids under 9 months, probably because it's kind of silly to have a baby who's just laying around all day wear suspenders. Are his pants really going to fall down? I think not.
Fortunately, there's a tutorial for everything, suspenders included. I asked around on Facebook for someone with a 4-6 month old to get some measurements for me, and sewed up some itty-bitty suspenders.
In the off chance that you should ever need to make tiny suspenders yourself, I cut the elastic pieces 21" long. I know my SIL thought they were funny, but I'm not sure if he's actually worn them (those buckles seem uncomfortable for a baby!), so I can't vouch for the fit.