I'm pretty sure no one sells a timing chain kit so your going to have to piece it together yourself
http://www.esatclear.ie/~bpurcell/318istimingchain.html
Upper timing cover gasket set 11141721919
Lower timing cover gasket set 11141721802
Front profile gasket (NOT the infamous one!) 11141247837
Rocker cover gasket set (only if the existing ones are old - they will withstand removal while the rubber is soft) 11121721876 profile gasket, 11121721475 spark plug chamber seal - lollipop shape, 3 off 11121721476 spark plug chamber - O shape)
Timing chain 11311247160
Crankshaft sprocket 11211247338
Camshaft sprockets (2 off) 11311721887
Front crankshaft oil seal 11141439570
Thermostat housing gasket 11531721172
Tensioner guide rail 11311727342
Guide rail 11311247470
2-3 litres of phosphour free antifreeze and 2 litres of water
If your timing chain tensioner is more than 4 years old you should replace it too - 11311743187 with its sealing washer 07119963355
waterpump and thermostat