Elixir Garden Supplies

https://elixirgardensupplies.co.uk/product/heavy-duty-plastic-tray-garden-growbag-carry-storage-household-5-sizes/

Standard & Deluxe Growbag Trays.

Ideal size for greenhouse use, these trays accommodate a full size grow bag and feature a series of horizontal ridges on the internal base of the tray which aid drainage and allow water flow under grow bags or plant pots. Suitable for use indoors and out, they keep water in and help prevent compost from spilling out.

Harrod Horticultural

https://www.harrodhorticultural.com/plastic-trays-only-pid7685.html?

These strong, watertight, multi-purpose plastic garden trays as used in our 'Self Watering' tray kits but can perform any number of useful garden tasks. The square trays can be used for general fetching and carrying, are ideal for moving seed trays about and the larger versions can be used with gravel or sand and soaked with water to aid watering and increase humidity in the greenhouse.

Garland Products (Growbag Tray)

https://www.garlandproducts.com/brochure/premium-growbag-tray-black.html

Ideally sized for grow bags, the tray features a series of shallow horizontal ridges on the internal base of the tray which aid drainage and allow water flow under grow bags or plant pots.

Made from recycled polypropylene.

Size Check: 100cm (39.5") Long 40cm (16") Wide 5cm (2") High External

Greenhouse People

https://www.greenhousepeople.co.uk/categories/accessories/trays/

Choose some useful garden trays from this collection. You can place these trays on top of your greenhouse staging and place plants in the trays for easier watering.

You can fill with capillary matting or Hortag or just leave empty and they can help prevent plants drying out or enable watering from the bottom.

Garden4less

https://www.garden4less.co.uk/shop-for/Self-Watering-Trays

We have designed these Self Watering Trays to make it easy for you to care for your plants - whether you are at home, at work or even on holiday.

For happy and healthy plants - these Self Watering Tray ensures your plants are kept correctly watered - not too much or too little. By watering into the watertight tray and not directly into the plant pots or seed trays, plants can control the amount of water they receive.