Alex Williams, 22, from Christchurch, had failed to appear in court for sentencing in November, but was arrested in the town on Sunday.
He appeared at Bournemouth Crown Court earlier and was sentenced to 20 months in prison for violent disorder.
Williams was also sentenced to a further two months for failing to appear in court.
Detectives had appealed to the public to help locate him after he failed to show up.
The gang's offences included throwing a liquid, thought to be ammonia, at two victims who were each left blind in one eye.
Four men were jailed for the attacks.
In November Joe Warne, 21, was sentenced to 20 years; Reece Watkins, 22, was sentenced to 18 years; Dominic Barker, 20, was given 16 years and Piers Fox-Havilland was jailed for 12 years.
The men, who lived in the London area, were also sentenced to 12 years for conspiracy to rob and eight for possession of imitation firearms - to run concurrently.
Dorset Police said the gang was charged following a lengthy investigation into attacks at locations including Boscombe and Christchurch.

Scotland's Information Commissioner has described proposed reforms to freedom of information law as setting a "worrying precedent".
Rosemary Agnew is due to give evidence to Holyrood's Finance Committee.
It is looking at changes to the Freedom of Information (Scotland) Bill.
As part of the reforms, ministers want to give an "absolute" exemption to communications between the Scottish government and senior members of the royal family.
At the moment, information about the Royal Family can be published in Scotland if it passes a public interest test.
Ministers want to remove that test thereby banning any release and bringing the situation in Scotland into line with legislation in other parts of the UK.
The amendment would exempt communications with the monarch, the heir to the throne or a member of the royal household acting on their behalf.
But in her response to the proposed changes, Ms Agnew said: "The amendment will create a provision which requires absolute secrecy in relation to any aspect of communications with senior royals in all circumstances - regardless of how far removed the information is from the content of communications, or of the weight of the public interest in favour of release.
"It is my considered view that it will... have the effect of unnecessarily restricting rights and create a worrying precedent with the introduction of a wide-ranging absolute exemption which sets aside the public interest.
"The amendment is therefore in direct conflict with the public interest."
Ms Agnew believes current protections for communications between ministers and the royals are sufficient.
A spokesman for the Scottish government said: "The amendment on correspondence on (or behalf of) Her Majesty provides for consistency of approach across the UK and in doing so ensures an appropriate level of protection for Scotland's current and future heads of state by safeguarding the well established conventions of confidentiality.
"Key elements of the Freedom of Information (Amendment) (Scotland) Bill include greater flexibility in reducing the lifespan of exemptions paving the way for more information to be made public earlier.
"The bill also makes the legislation stronger by making more effective the ability to bring a prosecution where requested information has been deliberately altered, destroyed or concealed."
A man who was part of a five-strong gang that committed violent acts in Dorset has been jailed.
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Plans by the Scottish government to keep any communication between ministers and the royal family secret are in direct conflict with the public interest, MSPs are to hear.