For the keyboard instruments below, I recommend birch handles for beginner players, to facilitate better control while developing technique. Rattan handles may be substituted, but are more expensive.
Bells: Mike Balter B10AB or BBB10

The 10AB is 7/8” phenolic, which is a hard plastic, similar to the mallets that come with student bell kits. Its smaller size help to not overpower the instrument (especially the shrill sounds from those student kits).

The BBB10 offers a 1” PVC ball, another hard plastic, and comes in at a lower cost than the 10AB.
Xylophone: Mike Balter B91B or BBB11

The B91B is a 1-1/8” poly, which is a softer plastic that is not as aggressive and harsh as the harder models and is suitable for xylophone (which is great if you want to minimize your collection).

The BBB11 is a cheaper version, but with 1” poly balls.
On a side note, both mallets for bells and xylophone are interchangeable. However, care must be given if using the hard plastics on xylophone. These hard mallets are capable of cracking wooden bars. With that in mind, I would recommend the poly mallets for both if you wish to minimize your collection.
Marimba: Mike Balter B13B or BBB2

Mike Balter’s Ensemble Series is the granddaddy of yarn mallets. Available in birch and rattan handles, the B13B (birch) is the medium model in the line of six.

The BBB2 is the cheaper version, only available with birch handles. The Basics series only offers 3 hardnesses (soft, medium, hard).
Vibraphone: Mike Balter B23B or BBB5

Mike Balter’s ProVibe Series is perhaps the most popular line of vibe (cord) mallets on the market. Like their sister Ensemble Series, this is the standard of cord mallets. The B23B is the medium model in the line of five, available in both birch and rattan.

The BBB5 again is the cheaper version, available with birch handles in soft, medium, and hard.
Rubber: Mike Balter B4B or BBB8

The B4B is the medium rubber mallet from Balter’s Unwound series, available in birch and rattan.

The BBB8 is the cheaper version, only available in birch, as you probably guessed by now.