In a live setting you'd plug into the PA so if you have a PA use it.
I've used an acoustic guitar amp (band leader loved this at practice), $50 used Ampex 2010 tube amp JBL speaker combo, Fearful bass cab with tweeters powered by Genz Benz head, $35 used Anchor Audio Xtreme 5500 powered PA with built in mixer. Mackie HR824 powered studio monitor which I bought for $10 because woofer had been replaced with KRK. Any of these works in moderate volume settings where a PA is not available.
So what I'm saying is that any full range PA type setup works. Many bass amps are basically PA. I wouldn't focus on a keyboard amp. Look more broadly for a good deal.