I just uploaded it, having got it from Wikpedia:
Cf. the Wikipedia entry for the house:
The alternative would be their royal seal, I suppose, but that's not really a symbol of the house. Thoughts?
Isn't the answer to consult the oracle?
There is no hurry, after all.
I did a little more looking this AM and this link may be iof interest.
The escutcheon was changed after the reign of the first stewart king, Robert II.
The answer is definately YES, on a Gold Shield a blue and white checkered Bar, Supporting the shield on either side are Crowned Rampant Lions. ( As displayed on the Royal Stardard off Scotland). on top of Shield a Helmet with a Red Plume.
An alternative might be the Clan Stewart badge.
The use of Royal seals and Coats of Arms (C.o.A.) must be with care as legal repercussions could ensue.
They are strictly attributable to one person or one family, with Royal seals and C.o.A.'s having similar rules within Royal Houses.
I have been working on the Categories: Clan Stewart | Clan Stewart of Appin | Clan Stuart of Bute | House of Stewart | House of Stuart and have shown many different C.o.A and there are many more described in the Heraldry of the Stewarts by George Harvey Johnston.
With respect to the answer from Mary Hammond there is no such thing as Clan Stuart (perhaps a spelling mistake?), there is a recognised Royal House of Stuart similar to the House of Hanover or Windsor.
Also there are only three "recognised clans" bearing the name Stewart/Stuart the "Clan Stewart", "The Stewarts of Appin" and "The Stuarts of Bute".
Have a look at the above mentioned Categories, they have changed and contain a lot of useful references.
Heraldry holds a great interest for me and further Study of https://en.wikipedia.org/wiki/house of stuart which states Stewart of Stewart for these arms, is incorrect as the Coat of Arms (C.o.A.) shown as Stewart of Stewart, is in fact the arms for the High Stewards of Scotland. See https://en.wikipedia.org/wiki/High_Steward_of_Scotland this is far clearer.
So the escutchen you propose to use would be fine for the House of Stewart (early Scottish Royalty) but not for the House of Stuart (Later Royalty of Great Britain) As yet I cannot see a suitable C.o.A. Perhaps you could use those of Henry Stuart Lord Darnley as the father of the first Stuart King.