I recently picked up a field monitor an andycine A6

https://www.amazon.com/ANDYCINE-A6-Monitor-1920x1080-Gimbals/dp/B077FNHBVF

I bought it used for about $80 there are cheaper field monitors but they have less resolution or less features. I took advantage of the fact my tripod has a 3/8ths thread at the bottom of the centre column so the bracket for the field monitor was screwed to that via a 3/8th to 1/4 male to male adapter. rather than being held in the hot shoe of the camera. it was about 2 and a half feet above the ground. Alternatively it could have been held by a "magic arm" clamped to the tripod it's very light weight so it wouldn't really affect the stability of the tripod.
My camera has a micro hdmi port which was connected by a hdmi cable to the hdmi port of the monitor, there is a small delay but it's not an issue, i just manually adjusted focus until i could see the focus peaking on the field monitor.

There is a more professional standard called SDI which is similar to hdmi but has less lag, however it's not commonly available in most consumer cameras. More expensive field monitors have more features such as time code recording the hdmi output passing out the hdmi output. But this is way beyond whats needed to take photographs and keep out the wet grass.

Another option might be a phone or tablet app and some form of tethering wired wireless or bluetooth, but my experience of this hasn't been very good. My ipad has the 'camera connection kit' so it may be possible to use a usb cable provided i can mount the ipad I do have a bracket with a 1/4 20 thread for iPad ( i have it on a light stand for piano lessons).

This photo was handheld using the back screen of the camera flipped to horizontal, it would have been easier with my rig.