Hi Dave,
it is difficult and not cheap to complete a helmet for an emblem. First, you need to find a helmet shell in good condition, which is the same model as your emblem and which has the same distance between the holes for the emblem attachment. Then you need to find a chinstrap or chinscales for it, as in most cases these are also missing. Finally, you‘ll need to find a pair of cockades, which are most likely missing too. So expect to pay €300 to €500 for the shell, €300 for the chinstrap (don't know if that's enough, because these chinstraps are extremely rare and very sought after). If you have an emblem M1886 emblem, you need to find chinscales in correct length, which is difficult to estimate. However, at around €180, these are a bit cheaper than the chinstraps. For the cockades you should calculate again about €160 (about €80 per side). In my opinion it is much easier and maybe cheaper to buy a complete helmet. You could place the emblem next to it, with a reference to the owner (if he is known or if it belonged to a family member) and that the complete helmet would have looked like this.
