Here's some additional info that may be of use…
RE: British Army policy on carrying regimental colours/standards into action at the time of the Sudan Campaign, Worgaimz is correct, this was officially banned in a circular sent to all infantry regiments on January 17, 1882 which ordered that, "In consequence of the altered formation of attack and the extended range of fire, Regimental Colours shall not in future be taken with the battalions on active service."
This was in reaction to the loss of the Queen's Colour from the 1st/24th and both the Queen's and Regimental colours from the 2/24th South Wales Borderers at Isandlwana in 1879 during the Zulu War, the loss of both the Queen's and Regimental colours of the 66th Berkshires at Maiwand in 1880 during the Second Afghan War, and then the near loss of the 58th Rutlandshires colours in 1881 at Laing's Nek, the first battle of the First Boer War, where the lives of several officers were lost in the process of saving the colours from capture by the victorious Boers.
That being said, if you have Perrys in your Sudan collection, prefer metal over plastic, and still want flags for your British Infantry units, then this pack of metal command figures from their "Victoria's Little Wars" range should serve you well, especially if you have troops wearing "Indian service dress":
Here's a LINK:
link
I myself would not deploy standard bearers with British troops in the Sudan, but neither would I hold it against anyone who likes the look of flags with all their units enough to do so. To each their own!