[dvd3500]

I have no idea who this guy is and I will not profit in any way but I saw this item when i searched for 2catch fencing" and thought it wasn't too terrible:
https://www.ebay.de/itm/Carrera-GO-Digit...Sw55FcOTAe
He took a sponge you use to get insects off the windshield and cut it into the shape he wanted and used a marker to draw bailing wire on it.

I am thinking some string would look more realistic and be almost as easy and at a cursory glance they don't look tooo bad.

Affixing them to the track may be trouble but I reckon double-sided tape should do it.

Maybe a dash of spray paint to get them a more realistic color...

[JasonB]

The twine is the wrong way round.

[JasonB]

Wine corks can also make half decent hay bales.

   

[Gordon Steadman]

Better than the foam

[JasonB]

Corks can also make rocks, or I guess gravel if you ground them up finer. Plus there is the added benefit of drinking the wine.

   

[Fluff]

Do you then forget why you ground up the corks ?

[JasonB]

No, but I did once break the kitchen blender by trying to jam too many corks into it. Flicked the switch, and ... crunch. Nasty noises, and broken blender. I hadn't even drunk any wine at that point.

[Talkingcars]

I stashed the old kitchen blender purely for scenery production when we got a new one.