I've had good luck with the generic "supcase beetle" ipad case on amazon:

https://www.amazon.com/SUPCASE-Unicorn-Full-body-Protective-Protector/dp/B06XWXTBFJ/ref=sr_1_3?ie=UTF8&qid=1516312589&sr=8-3&keywords=ipad+case+beetle

Had it for a few years, iPad has been with me out to a lot of jobs, dropped a lot and held up just fine. The otterbox ones seem to be the same quality and cost about double depending on the model.