DT Brown - Pro Seeder

https://www.dtbrownseeds.co.uk/Garden-Essentials-1/Sowing-and-Propagation/Pro-Seeder_5.html?

Sow seeds one at a time

A great little gadget that allows you to sow seeds of all shapes and sizes one at a time.

No seed is wasted and it reduces the need for thinning out seedlings later. Able to use on all seeds. Instructions include a key diagram, to show you which nozzle to use when sowing seed. Works on a suction method. Full, easy-to-follow instructions are included.

Gardening Naturally

https://www.gardening-naturally.com/magic-seeder?

Designed especially for planting small vegetable and flower seeds, this great little tool used by the Royal Horticultural Society is ideal for accurate sowing of seeds in a compact plant trainer, plug trays, pots or seed trays.

Simple and easy to use it will cope with seeds up to 2mm in size.

Seed Spacing Ruler

https://www.gardening-naturally.com/seed-and-plant-spacing-ruler

Takes the guesswork out of seed spacing. Amazingly handy rule with seed sowing holes, metric and imperial graduations, plus printed vegetable spacing guide. Precision machined from FSC beech wood.

Two sizes available:

Small - 32cm

Large - 100cm (1m)